To develop criteria that identify patients likely to benefit from regenerative therapies, it is important to identify functional indices associated with improved outcomes. Analysis from some trials support the importances of cell and patient characteristics in predicting clinical outcomes. In FOCUS-HF (First Bone Marrow Mononuclear Cell United States Study in Heart Failure) assessing effects of intramyocardial autologous bone marrow mononuclear cells in patients with no option chronic heart failure, younger patients (≤60 years)  had significantly higher numbers of mesenchimal progenitor cells  versus those >60 years. Younger patients also had significant improvement in maximal oxygen consumption (VO2 max) versus age-matched reference subjects while older patients did not, identifying age as an important modifier of therapeutic effect.